JPH01215741A - Enamel coating mixed with glass beads for cooking utensil and coated utensil - Google Patents

Abstract

PURPOSE: To improve thermal impact resistance and wear resistance by fixing glass beads, etc., in a prescribed state onto the outermost layer and intermediate layer of cooking utensils to which three layers of enamel layers are applied.

CONSTITUTION: The first enamel layer 7 is applied on the bottom 1 of the cooking utensil and is then dried. The second enamel layer 3 is applied on this enamel layer 7 by a screen process. Further, the enamel layer 3 is coated thereon with the noncontinuous third enamel layers 4 and is decorated. The three layers 7, 3, 4 are obtd. by enamel frit and is simultaneously fired. The enamel layer layers 3, 4 contain the glass beads 5, 6 and some thereof have the diameter larger than the thickness of the enamel layers described above and project from the surface of the layers 3, 4. Some of the beads 6 in the third layer 4 are adhered onto the beads 5 in the second layer 3. The layer 3 contains thermally conductive flakes 9. These flakes 9 are arrayed in parallel with the surface.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides cooking utensils such as frying pans, stew pots,
Concerning the enamel coating around the bottom of shallow steamed pans, etc.

The invention also relates to cooking utensils provided with an enamel coating of this type.

As disclosed in French patent no. 2.544.338,
Known coatings around the bottom of cooking utensils comprise a first enamel layer that completely covers the bottom of the utensil. On top of this layer is formed a second discontinuous layer of enamel which constitutes a decorative surface which is applied by a screen process after drying of the first enamel layer. The two layers are obtained from enamel frit and fired simultaneously.

The simultaneous combustion of the two enamel layers makes it possible to obtain a strong bond of the two layers and excellent resistance to the severe thermal shocks to which the enamel coating is exposed.

The discontinuous outer layer that constitutes the cosmetic not only improves the appearance of the bottom of the appliance, but also constitutes a wear layer that protects the underlying enamel layer against impact and abrasion.

In fact, increasing the surface of this decorative layer allows it to be worn away without detracting from the beautiful appearance of the enamel coating.

Nevertheless, due to the discontinuous nature of the outer enamel layer, this layer can be removed too quickly, especially if this enamel is obtained from an enamel frit for aluminum, which is clearly less hard than the enamel for steel or cast iron instruments. wear out.

In order to provide a countermeasure for this relatively low hardness and to increase the resistance to abrasion of the outer enamel layer with a thick surface, the applicant has proposed in FR 2.544.338 a material such as e.g. It was proposed to fill this enamel layer with hard particles having an angular shape such that some of the particles protrude from the surface of the enamel layer.

However, this hard and angular particles protruding from the enamel surface considerably increases the coefficient of friction of this surface,
This is quite difficult to clean.

Additionally, when worn, these particles can give thick surface enamels an unattractive appearance.

Additionally, because of its insulating properties, enamel coatings impede heat transmission through the bottom of the cookware.

- The aim of the invention is to overcome these disadvantages of said enamel coatings.

The present invention relates to an enamel coating for cooking utensils, which is coated with an enamel layer of discontinuous layer 3 constituting the decoration and the bottom is covered with a second enamel layer applied by a screen process after drying of the first layer. It comprises a partially coated first enamel layer, the three layers being obtained from an enamel frit and fired simultaneously.

According to the invention, said enamel coating comprises a second as well as a third enamel layer comprising glass beads, a certain number of which has a diameter of a value greater than the thickness of said enamel layer and protrudes from the surface of said layer. a certain number of beads of the layer of non-continuous layer 3 are deposited on the beads of the second layer, the second enamel layer being arranged in a direction parallel to each other and said layers and partially overlapping each other. Distinguished by the inclusion of thermally conductive flakes.

Glass beads protruding from the surface of the discontinuous outer layer are
It makes it possible to increase the resistance to abrasion of the outer layer and to reduce its coefficient of friction, so that the outer layer is easily cleaned and does not present a sensitive surface.

Furthermore, the applicant has surprisingly found that despite its smooth surface, which is unfavorable for the fixation of glass beads in enamel, by applying a discontinuous outer layer by a screening process said beads are firmly fixed. discovered. In practice, screen process deposition consists of applying the enamel paste through the mesh of the screen by squeezing and penetrating the beads into the enamel layer.

Furthermore, the penetration of the beads into the non-continuous outer layer is controlled by the presence of glass beads in the underlying enamel layer, at least a certain number of beads of the outer enamel layer being applied.

Furthermore, the glass beads present in the underlying enamel layer make it possible to increase the abrasion resistance and facilitate the cleaning of the part of said layer that is not covered by the discontinuous layer.

A parallel arrangement of flakes is obtained by the action of the screen process squeeze.

The flakes are oriented in a direction parallel to the surface of the enamel layer and form a thermally conductive screen therein which homogenizes the heat distribution over the bottom surface of the appliance and considerably increases heat transfer through the enamel coating.

The association of the continuous second enamel layer and the discontinuous third enamel layer can provide effects that cannot be obtained with a single layer containing both beads and flakes.

In fact, flakes cannot be mixed into the non-continuous third layer. This is because in this case the bonding of the layers is insufficient.

Furthermore, thermal properties are not improved due to the discontinuous nature of this layer. This characteristic l is obtained only when the continuous second layer contains flakes.

Preferably, a second enamel layer is also applied by screen process deposition. This makes it possible to precisely adjust the depth of penetration of the glass beads into the first enamel layer.

In a preferred embodiment of the invention, the maximum diameter of the beads is twice the thickness of the enamel layer.

All glass beads are placed in the enamel layer to a depth at least equal to their diameter, ensuring that they are fixed in the enamel layer.

In an advantageous embodiment of the invention, the diameter of the glass beads is in the range from 5 to 40 μm, and the average diameter of said beads is in the range from 15 to 20 μm.

The thickness of each enamel layer is within the range of 20-25 μm.

Preferably, each enamel layer contains 5-20% by weight of glass beads.

Below 5% glass beads, their effect on the properties of the enamel is negligible, while above 20% the bond between beads and enamel is impaired.

Preferably, the second enamel layer contains 2 to 10% by weight of flakes.

This effect is negligible when flakes are less than 2%, and -10%
In this case, its presence causes damage to the bonding of the enamel layer.

This frame is preferably made of TiO□ and/or Fe.
Made of mica coated with a thin layer of tOx. It has a copper-like color and gives the enamel coating a very beautiful appearance.

The second and third enamel layers are preferably made of talc, for example.
graphite, molybdenum disulfide, vanadium disulfide,
It includes solid particles of plate-like structure with lubricating properties such as boron nitride and mixtures thereof.

Particles with a plate-like structure moderately lower the coefficient of friction of the enamel coating and considerably reduce the frictional effect of the cooking plate of the utensil.

In the case of a discontinuous outer layer, the lubricating particles complete the action of the bead and are removed from the bead when the layer is worn to the surface.

In the drawing, for example an aluminum bottom 1 of a cooking vessel with an internal surface (i.e. a food contact surface) coated with anti-stick N2 of polytetrafluoroethylene, for example.
shows.

The external surface of the sole l is coated with an enamel coating according to the invention and consists of three layers 7, 3 and 4. The first enamel layer 7 covers the entire external surface of the appliance, while the two enamel layers 3 and 4 are applied only to the bottom 1 part of the appliance.

The three enamel layers 7.3 and 4 are 500-600°
It is obtained from an enamel frit which can be sintered at a temperature of C, ie a temperature compatible with the melting point of aluminum.

The first layer 7 is applied by spraying from an aqueous slurry of enamel or rufrite. A second enamel layer 3 as well as a third enamel layer 4, which is discontinuous and constitutes a thick surface decoration, are applied by screen process deposition after drying of the first layer 7, and the three layers are fired simultaneously.

the two enamel layers 3, 4 contain glass beads 5.6;
A small number of the beads 6 of the outer layer 4 have a diameter of a value greater than the thickness of said enamel layer 3.4 and protrude from the surface of this layer. It is clear from Figures 1 and 2 that beads 5 are coated.

During application by the screen process, the paste containing the enamel frit and beads 5 and 6 is squeezed through the mesh of the screen and the beads 5.
6 into each enamel layer. In this way, the beads 5 of the second layer 3 rest on the first enamel layer 7,
- the beads 6 of the layer 4 of the force cylinder 3 rest on the beads 5 of the second layer 3;

The maximum diameter of the bee x5.6 is 2 times the thickness of the enamel layers 3 and 4.
It's double.

The diameter of said beads 5.6 is preferably in the range from 5 to 40 μm, the average diameter thereof is in the range from 15 to 20 μm, while the thickness of each enamel layer 3.4 is preferably from 20 to 40 μm.
It is in the range of 25 μm.

Therefore, a certain number of beads (5.6
．． It protrudes from the surface of 4. The beads 5.6 are completely fixed within the enamel.

Each enamel layer 3, 4 contains 5-2% by weight of glass beads.

During the application of the third enamel layer 4, the beads 6 cannot penetrate into the second enamel layer 3, since the beads 5 limit the depth of penetration of the beads 6. Glass beads 6 in external enamel layer 4
provides resistance to abrasion and thus protects the aesthetic appearance of the thick surface finish formed by said 114.

Furthermore, due to its smooth protective surface, the beads 6 impart anti-adhesive properties to the enamel N4, which considerably facilitates the cleaning of this layer.

In addition to the properties mentioned above, the beads 5 protect the parts of the enamel layer 3 not covered by the discontinuous layer 4 from abrasion and at the same time facilitate the cleaning of those parts.

Said second enamel layer 3 contains particles 9 in an amount of 2 to 10% by weight. This flake 9 preferably consists of a mica strip coated with a thin layer of TiO2 and/or Fe,01, giving it a copper-like metallic appearance.

The flakes 9 have lengths ranging from lO to 10 um and 2
It has an average thickness on the order of μm. The parallel arrangement of flakes 9 is obtained by the action of the squeeze used to apply the enamel layer 3.

The flakes 9 have the following effects.

On the one hand it increases the thermal conductivity of the enamel coating and homogenizes the heat distribution over the surface of the bottom l of this appliance, and on the other hand it increases the resistance of the enamel layer 3 to contamination; in fact
The screen formed by the flakes 9 is the enamel layer 3
Masks impurities that have entered the pores of the

The two enamel layers 3.4 preferably further contain solid particles of lamellar structure with lubricating properties, such as for example talc, graphite, molybdenum disulfide, vanadium disulfide, boron impuride, etc. and mixtures thereof.

This lubricating property facilitates the application of the enamel layer 3, 4 by the screen process and increases its anti-adhesive properties.

One example of a practical application of an enamel coating according to the invention is shown below.

To form the first layer 7, the external surface of the device is sprayed with an enamel frit slurry. After drying of this first layer 7, a second enamel N3 is applied onto the first layer of the sole 1 by screen process deposition. This second layer is in the form of an oily paste and contains:

a) For example, 34% Sing 20% Na20 20 to 10% 2% Li, 0 20% TiO□ 2% AlzO+ 2% P2O.

100 parts by weight of enamel frit for aluminum containing 10% v20°; b) 0 to 0 inorganic pigments that withstand temperatures of at least 600°C
5 parts; c) TiOz and F, 0. coated with 10~
Mica flakes 2-10 with length ranging from 708m
part; d) diameter ranging from 5 to 40 μm (with an average diameter of 15 to 40 μm);
5 to 2 glass beads with a diameter of 20 μm)
0 parts; e) 25 to 45 parts of pine oil: f) Talc, graphite or molybdenum disulfide 2
~10 parts.

This layer dries. After drying, the dry enamel biscuit thus obtained has a thickness of the order of 25-30 μm.

On this enamel biscuit, an enamel layer of discontinuous tubes 3 having the same composition as the second layer but without flakes is applied by a screen process.

The third enamel layer thus obtained is simultaneously fired at a temperature of the order of 550'C.

The enamel coating thus obtained is susceptible to thermal shock (4
It has excellent resistance to heating to 00°C and subsequent immersion in cold water.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of the bottom of a cooking utensil provided with an enamel coating according to the invention, and FIG.
It is an enlarged view showing details of. 1... Bottom, 2... Anti-adhesion layer, 3...
- Second enamel layer, 4... Third enamel layer, 5.6... Glass beads, 7... First enamel layer, 9... Flake.

Claims (1)

Claims: 1. Covered with a non-continuous third enamel layer (4) constituting the makeup and with a second enamel layer (3) applied by a screen process after drying of the first layer. Enamel coating for cookware, comprising a partially coated first enamel layer (7), the three layers (7,
3, 4) are obtained from the enamel frit and burned at the same time, the second and third enamel layers (3, 4) comprising glass beads (5, 6), of which at least a certain number is larger than the thickness of said enamel layer. a non-continuous third layer bead (6) having a diameter of a large value and protruding from the surface of said layer;
are deposited on top of the beads (5) of a second layer (3), the second enamel layers (3) being arranged in a direction parallel to each other and to the surface of said layers and partially overlapping each other. An enamel coating comprising thermally conductive flakes (9). 2. Enamel coating according to claim 1, wherein the second and third layers (3, 4) are applied by a screen process. 3. The maximum diameter of the beads (5, 6) is the enamel layer (3, 4
2. The enamel coating of claim 1, wherein the enamel coating is twice the thickness of ). 4. Enamel coating according to claim 1, wherein the diameter of the glass beads (5, 6) is in the range from 5 to 40 μm, and the average diameter of the beads is in the range from 15 to 20 μm. 5. The thickness of the second and third enamel layers (3, 4) is 2
5. Enamel coating according to claim 4, which is in the range of 0 to 25 μm. 6. Each enamel layer (3, 4) contains 5-20 glass beads
The enamel coating of claim 1, comprising % by weight. 7. The second enamel layer (3) has 2 to 1 flakes (9)
2. Enamel coating according to claim 1, comprising 0% by weight. 8. Frame (9) is TiO_2 and/or Fe_
Claim 1: Made of mica coated with a thin film of 2O_3.
Enamel coating as described. 9. Flake (9) has a length of 10-70 μm and 2 μm
2. Enamel coating according to claim 1, having an average thickness of the order of m. 10. Enamel coating according to claim 1, wherein the two enamel layers (3, 4) contain solid particles of lamellar structure with lubricating properties. 11. Solid particles with lamellar structure are talc, graphite,
Enamel coating according to claim 1, selected from molybdenum disulfide, vanadium disulfide, boron nitride and mixtures thereof. 12. A cooking utensil provided by the enamel coating of claim 1.